Sadly, doctors are almost certain that the cancer will return and the money is needed for 'relapse treatment'.

But he may have been given a lifeline by doctors who have come up with a groundbreaking treatment that will cost £140,000 - but Kian's family have to come up with the money in 30 days.

Mum Kat said: "This has left me facing the hardest decision of my life. If I spent the money we've raised on the new, preventative treatment, and it doesn't work, I'm left with nothing.

"But I couldn't live with myself if I let this new opportunity pass."

The ground-breaking new treatment, called DFMO, aims to prevent the cancer's return by stopping a cell that creates the neuroblastoma cell.

But the treatment can't be started any later than 120 days after the patient last underwent immunotherapy and Kian's last treatment finished 90 days ago.

Kat said: "That leaves me with hardly any time to apply and raise the money.

"The trial is taking place in New York, so we'd be flying over there every three months for a two-year period.

"I can use the £100,000 already raised towards this, but I need to keep fundraising because, if this doesn't work, I'll still need £500,000 towards the relapse treatment."

Kian was first diagnosed with stage four neuroblastoma in 2013, and battled against 27 different tumours attacking his body. The disease first attacked his nerve cells, before travelling around his tiny body and spreading to his bones.

But while the family were delighted when the disease was finally beaten eight months later, medics revealed there was an 80 per cent chance that the disease would return.

Kat added: "I want to give my boy every chance of survival, I'm sure any other mother would be the same. I'm scared that if I let go of this opportunity, I'll forever regret it. But then if it doesn't work, I could be left with nothing."

Remarkably, medics at the New York clinic where the treatment is performed have said that out of 55 children who have taken part in the trial, just four have suffered a relapse.